GemNotes

GIA CHART HELPS IDENTIFY SYNTHETIC DIAMONDS

The Gemological Institute of America, with assistance from De Beers, has produced an elaborate photo chart to help diamond dealers and jewelry retailers distinguish synthetic diamonds from natural ones.

“Small numbers of gem-quality synthetics have begun appearing in the jewelry industry,” says Dr. James Shigley, GIA’s head researcher, in a related article in Gems & Gemology, the institute’s quarterly magazine. “It has become critical that the professional jeweler or dealer have the skills to identify natural, untreated diamonds.”

The chart lists what to look for using standard gemological equipment and is organized into three color groups – yellow, colorless and blue.

Each color group is subdivided into four categories of identifying properties: general, including color, size and shape of rough crystals; features seen by magnification; fluorescence to ultraviolet radiation; and miscellaneous, including luminescence, electrical conductivity and ability to be attracted by a magnet.

Shigley says all known synthetics and treated synthetics can be identified based on the information presented in the chart.

Here are some highlights, listed by color group.

Yellows: These comprise the most commonly produced diamond synthetics. Characteristics include:

  • Internal color distribution. This is often even in naturals but rarely so in synthetics. Some naturals have uneven color distribution, but the darker zones tend to be irregularly shaped rather than symmetrical as in synthetics. Irradiated natural polished diamonds often show color zoning that follows the faceted shape of the diamond.

  • Inclusions. These can differ greatly. Synthetics often have round or elongated metallic or opaque black inclusions of flux metal. Sometimes these inclusions appear in small groups.

  • Fluorescence. Naturals almost always fluoresce evenly; synthetics never do. This is not a positive test in itself, however, because some naturals do fluoresce unevenly.

  • Attraction by a magnet. No natural yellows are known to have been attracted by a magnet. However, a strong magnet may attract some synthetics because of the metallic inclusions left from the growth process.

Colorless: Colorless synthetics are much rarer than yellow ones because they are harder to grow “cleanly.” Still, attractive rough of up to 3 carats has been produced. Here are some characteristics:

  • Graining. Naturals usually have graining along planes parallel to or crisscrossed with the rough crystal face. Most colorless synthetics have little or no visible graining.

  • Inclusions. These are similar to those in yellow synthetics.

  • Fluorescence. Naturals usually fluoresce evenly; synthetics never do.

  • Attraction by a magnet. Some colorless synthetics may be attracted to a magnet.

  • Electrical conductivity. Some types of naturals (Type IIb) are electrically conductive while synthetics are not.

Blues: Some characteristics of blue synthetic diamonds are similar to those of yellow ones:

  • Internal color distribution. This is often even in naturals but rarely so in synthetics. Synthetics often show a cross-shaped color zoning pattern while naturals can show an indistinct blue-colorless zoning.

  • Graining. Synthetics can show a curious stop-sign-shaped graining pattern. Graining in naturals is rare, but when it occurs, it has a whitish appearance.

  • Inclusions. These can differ greatly. Synthetics often show rounded or elongated metallic or opaque black inclusions of flux metal. Sometimes they appear in small groups.

  • Fluorescence. Natural blues usually fluoresce evenly, but synthetics fluoresce along internal growth sector arrangements, creating geometric patterns.

  • Strain (anomalous double refraction). Synthetics usually show a black or gray cross-like pattern. Naturals have banded or cross patched patterns of numerous colors.

Step-by-step process: The article in G&G says that when using the chart, a diamond dealer or jewelry retailer first should examine the diamond under magnification for telltale inclusions, color zoning and graining. (GIA recommends a gemological microscope.)

Second, examine the diamond face up under ultraviolet light. Look for telltale patterns and the relative strength between longwave and shortwave fluorescence.

Third, examine the diamond’s spectrum with a spectroscope and check whether it reacts to a strong magnet.

Finally, if necessary, check the strain patterns with crossed polarized filters in a gemological microscope.

Effect on industry: Synthetic diamonds of a size and quality suitable for faceting have been grown in limited numbers, says Shigley, but have had little, if any, adverse impact on the jewelry industry.

GIA has encountered 13 synthetics in the past nine years. Of those 13, 10 were yellow and three were red, colored by laboratory treatment. The article doesn’t indicate whether these were submitted by people who knew they were synthetics. However, some reports say the three red diamonds were submitted as naturals and flagged by the GIA graders. (The graders now routinely test whether a diamond is natural or man-made.) Shigley says other gem labs also have encountered synthetics, many of them from Russia.

The chart and G&G article can be obtained from GIA, P.O. Box 2110, Santa Monica, Cal. 90404; (800) 421-7250 or (310) 829-2991. For more information on synthetic diamonds, see “Synthetic diamond jewelry: Are you prepared?” March JCK, page 47.)

ICA PUTS GEMS ON THE INTERNET

The International Colored Gemstone Association (ICA) recently launched its new Gemsite, a World Wide Web site on the Internet. The announcement was made by ICA’s President, Paolo Valentini, and by ICA’s GemBureau Director, Cheryl Kremkow, during the Tucson gem and mineral show in February. The Internet address is http://www.gemstone.org.

ICA claims Gemsite is the largest and most comprehensive jewelry industry website on the Internet. It contains information about specific gemstones (at least 30 different gems from amethyst to zircon are profiled), gemstone localities, buying tips, jewelry fashion, gem history and lore, as well as import and export statistics. Some 50 gemstone photos are available to download.

Kremkow, who developed Gemsite, feels it can help build marketing confidence and promote ICA’s position as a reputable, ethical body. It has the potential to reach millions of consumers and retailers. (There currently are an estimated 12 million on-line users with access to the Internet.)

“This is an excellent target market,” says Kremkow “because user incomes are around $80,000 per year, and they are in the 35 year old and above age bracket. Also the audience is pre-selected, because a person who already as an interest in gems would be the one tapping in to the Gemsite.”

What future projects are planned for Gemsite? Says Kremkow: “Gems in the Bible or Gems in Shakespeare may be included. But we want to keep the information fresh. It will be changed regularly.”

IT ISN’T BROKEN, SO DON’T FIX IT

Any gemstone cutter simply has to love minerals and crystallography. Years of studying crystal growth markings (such as striae and etch marks) and crystal structure become guideposts used to determine how a particular gemstone should be cut. But what happens if the cutter falls in love with the growth markings themselves?

Phillip Becker of Idar-Oberstein, Germany, has done just that. While he still gently forms gem material at his cutting wheel, he now lets the nature of the gem dictate the cutting rules. If the gem has unusual striae or growth marks, for example, he will incorporate these whimsically in the final product. Becker may leave natural depressions and pits in the pavilion, and polish a table and crown facets. The result? A sort of natural, bizarre “internal carving” or reverse intaglio.

Obviously this isn’t a gemstone for the mass market. It is ideal for designers who want a unique product and consumers seeking something a bit “rough around the edges” that may say something specific about them.

The gems (mostly aquamarine, green beryl, heliodor and morganite) are distributed through James Alger Co., Manchester, N.H.; (603) 625-5947.

GEM ARTISTS OF NORTH AMERICA, UNITE!

Gem carvers, cutters and ornamental artists from around the United States met during the recent Tucson gem and mineral shows. Their goal: to form an association that will give them a united voice, political and marketing clout and a chance to share ideas.

The meeting was fiery at times. But attendees officially adopted the name Gem Artists of North America or GANA (which had been used informally since the group’s exploratory meeting a year ago) and decided just what gem artists are. The final consensus: “We are a people whose profession is working in gem materials in a creative manner.”

That bit of self-analysis may seem obvious, but it defines who will be eligible for membership. There was some disagreement, for example, about whether ornamental alabaster carvers or traditional mass cutters would qualify. In the end, it was agreed that GANA firm membership would be limited to those who work with gem materials with a Mohs hardness of at least 5. Members must be professional gem artists (although not necessarily working full time). Affiliate membership would be open to people who support the gem arts in some way, members of the press, agents, hobbyists and students.

Gem carver Arthur Anderson, who edits a newsletter for GANA, says a board of directors will be formed to establish a written charter and mission. GANA’s next meeting will be held in Tucson next February.